Apparatuses and methods for tuning center frequencies

Abstract

Apparatuses and methods for tuning center frequencies are described herein. Examples of tuning described herein including tuning using feedback from the resonator. Variable gain feedback for tuning of acoustic wave resonators is provided in some examples. An example apparatus may include a resonator and a feedback loop. The resonator may be configured to receive a tuning signal and to provide a feedback signal. The feedback signal may be based on the tuning signal. The feedback loop may be configured to receive the feedback signal from the resonator. The feedback loop further may be configured to provide the tuning signal to actively tune a center frequency of the resonator. The tuning signal may be based on the feedback signal.

What is claimed is: 
     
       1. A method for tuning an acoustic wave resonator that includes a plurality of radio-frequency (rf) transducer electrodes, comprising:
 in a feedback loop, receiving a feedback signal from one or more of the rf transducer electrodes; 
 phase shifting the received feedback signal to provide a phase shifted feedback signal having a phase shift; 
 amplifying the phase-shifted feedback signal to provide a tuning signal; and 
 returning the tuning signal to one or more of the rf transducer electrodes; wherein: 
 the method further comprises applying a control signal to a variable gain amplifier for actively tuning the acoustic wave resonator; 
 the amplification of the phase-shifted feedback signal is performed, at least in part, in the variable gain amplifier in response to the control signal; 
 the tuning signal is returned to the one or more said rf transducer electrodes with the said phase shift; 
 the plurality of rf transducer elements comprises a feedback group, a tuning group, an input group, and an output group, each said group consisting of one or more rf transducer electrodes unshared with any other said group; 
 the feedback signal is received in the feedback loop from the feedback group; 
 the tuning signal is returned to the tuning group; 
 the method further comprises applying an input signal to an input port connected to the input group; and 
 the method further comprises obtaining an output signal from an output port connected to the output group. 
 
     
     
       2. The method of  claim 1 , wherein the tuning signal comprises a differential signal including a plurality of complementary signals and wherein returning the tuning signal comprises:
 providing a first complementary signal of the plurality of complementary signals to a first rf transducer electrode of the resonator; and 
 providing a second complementary signal of the plurality of complementary signals of the tuning signal to a second rf transducer electrode of the resonator. 
 
     
     
       3. The method of  claim 1 , wherein phase shifting the received feedback signal to provide a phase shifted feedback signal comprises phase shifting the received feedback signal by −90 degrees. 
     
     
       4. The method of  claim 1 , further comprising attenuating the tuning signal responsive to the tuning signal exceeding a threshold. 
     
     
       5. An apparatus having a resonant frequency that is tunable in response to a control signal, comprising:
 an acoustic wave resonator that includes a plurality of radio-frequency (rf) transducer electrodes; and 
 a feedback loop configured to receive a feedback signal from one or more of the rf transducer electrodes, process the received feedback signal so as to create a tuning signal, and return the tuning signal to one or more of the rf transducer electrodes; wherein: 
 the feedback loop comprises an element for imparting a phase shift to the feedback signal so as to provide a phase-shifted feedback signal; 
 the feedback loop further comprises a variable gain amplifier configured to amplify the phase-shifted feedback signal according to a gain controlled by the control signal, thereby to actively tune the resonant frequency; 
 the tuning signal is returned to the one or more said rf transducer electrodes with the said phase shift imparted by the phase-shifting element; 
 the plurality of rf transducer elements comprises an input group, an output group, a feedback group, and a tuning group, each said group consisting of one or more rf transducer electrodes unshared with any other said group; 
 a signal input port is connected to the input group; 
 a signal output port is connected to the output group; 
 the feedback loop receives the feedback signal from the feedback group; and 
 the tuning signal is returned to the tuning group. 
 
     
     
       6. The apparatus of  claim 5 , wherein the feedback loop further comprises:
 an amplifier coupled to the variable gain amplifier and configured to receive the amplified signal and to provide the tuning signal, the tuning signal based on the amplified signal. 
 
     
     
       7. The apparatus of  claim 6 , wherein the phase-shifting element is configured to phase shift the feedback signal such that the feedback signal is reactive. 
     
     
       8. The apparatus of  claim 6 , wherein the amplifier coupled to the variable gain amplifier comprises a differential amplifier. 
     
     
       9. The apparatus of  claim 6 , wherein the variable gain amplifier is configured to adjust amplification of the phase shifted feedback signal in real-time. 
     
     
       10. The apparatus of  claim 5 , wherein the tuning signal comprises a differential signal. 
     
     
       11. The apparatus of  claim 5 , wherein the resonator is configured to provide a current-based feedback signal,
 an amplifier coupled to the resonator is configured to convert the feedback signal from a current-based signal to a voltage-based signal; and 
 the apparatus further comprises a voltage limiter coupled to the current-to-voltage-converting amplifier and configured to receive the voltage-based feedback signal, the voltage limiter further configured to attenuate the voltage-based feedback signal responsive to a magnitude of the voltage-based feedback signal exceeding a threshold to provide the tuning signal. 
 
     
     
       12. An apparatus having a resonant frequency that is tunable in response to a control signal, comprising:
 an acoustic wave resonator that includes a plurality of radio-frequency (rf) transducer electrodes; and 
 a feedback loop configured to receive a feedback signal from one or more of the rf transducer electrodes, process the received feedback signal so as to create a tuning signal, and return the tuning signal to one or more of the rf transducer electrodes; wherein: 
 the feedback loop comprises an element for imparting a phase shift to the feedback signal so as to provide a phase-shifted feedback signal; 
 the feedback loop further comprises a variable gain amplifier configured to amplify the phase-shifted feedback signal according to a gain controlled by the control signal, thereby to actively tune the resonant frequency; 
 the tuning signal is returned to the one or more said rf transducer electrodes with the said phase shift imparted by the phase-shifting element; 
 the plurality of rf transducer elements comprises an output group, an internal feedback group, an external feedback group, and a tuning group, each said group consisting of one or more rf transducer electrodes unshared with any other said group; 
 the output group is connected to an input of a transimpedance amplifier; 
 an output of the transimpedance amplifier is connected to an output port; 
 the output of the transimpedance amplifier is connected to the internal feedback group; 
 the feedback loop receives the feedback signal from the external feedback group; and 
 the tuning signal is returned to the tuning group. 
 
     
     
       13. The apparatus of  claim 12 , further comprising a voltage limiter connected between the output of the transimpedance amplifier and the output port and configured to attenuate signals exiting the output of the transimpedance amplifier responsive to a magnitude of the voltage-based feedback signal exceeding a threshold to provide the tuning signal.